Apparatus for cracking reduced crudes and the like



June'28, 1932. N E. LOOMls 1,865,027

APPARATUS FOR CRACI-{ING REDUCED CRUDES AND THE LIKE Filed March lO,1926 2 Sheets-Sheet 1 f gA b 1 .N h Q 2 L S 03 N n w "V if il l N l\ Q Lm w 1g 1- lo 0 N N 0* l ,f xo. N

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APPARATUS FOR CRACKING REDUCED cRUDEs AND THE LIKE Filed March 10, 19262 Sheets-Sheet 2 l3c/msu? To WER cc UMULA TOR Ffa; -2

N {An-wwwa L Looms Juve/nto@ @ZM @Howe/1g l coil 23 arranged in aPatented June 2.8,'` 1932( UNITED STATES PATENT oFF-ICE NATHANIEL E.LOOMIS, OF 'WESTFIELD, NEW JERSEY, ASSIGNOR T0 STANDARD OIL YDEVELOPMENT COMPANY, A CORPORATION OF'DELAWARE APIPARAT-US FOR CRACKINGREDUCED CRUDES AND THE Application iled March 10, 1926. Seria No.93,597.

This invention relates to improvements in processes and apparatus forthe cracking of hydrocarbons intovl lower boiling products. ,Theinvention will be fully understood from the following description, takenin connection with the accompanying drawings, in

which Fig. 1 is a diagrammatic elevation of one suitable form ofapparatus, and

Fig. 2 is a plan view of the same.

Referring to the drawings, reference numeral 1 denotes a shell still orequivalent distillation/or vapor-separating means, arranged in a furnacesetting 2. The still 1 is preferably provided with internal horizontalflues 3, through which hot combustion gases from the furnace pass to astack, not shown. The still is connected through line 4 with condensingand fractionating equipment, such as a bubble tower 5. This tower hasthe usual plates 6, receiving pan 7, vapor Vheat exchanger 8, vapor line9, and condenser 10.

A condensate draw-off line 11, having a valve 12, conveys a fraction ofthe type of gas oil from Athe pan 7 to an accumulator tank 13. A line 14serves to supply cooling fluid (ordinarily feed stockfor the system) tothe vapor heat exchanger 8. A by-pass 15 in line 14 and valves 14', 15',are provided for the regulation of the supply of feed stock. Additionalpreheat may, be supplied in an exchanger 8', which receives the gas oilfrom the pan 7. Suitable by-pass lines are provided leading to exchanger8',-as shown.

A line 16 carries the preheated feed stock to a tar heat lexchanger 17which is supplied with hot tar from the still 1 through line 18, havinga valvr19. The feed stock passes through the through pipes 20 and 21, inthe latter of which a'pump 22 is installed, to a cracking furnacesetting 24. Tar is withdrawn from the tar heat exchanger through 'valvedline 25 to storage tar heat exchanger and thencel drums 27 and 28, inaccordmore drums maybe operated in series, the

parallel arrangement 4 illustrated is preferred. Draw-oil' pipes 33 and34 connect drums 27 and 28 respectively to a pipe 35 which dischargesinto the still 1.

A pressure release valve 36 is provided in pipe 35. The coil .and drumsare to be operated at relatively high pressure, as is well understood inthe art, and the drums should be thermally insulated as by means of alagging 37, or in some other suitable way.4

The present invention is Aparticularly adapted to the treatment ofreduced erudes,

ffor reasons which will be fully presented later. The following example,therefore, is based upon the use of such a stock, though it is to be`understood that the invention is not limited thereto.

Assuming the system to be in operation, a stream of reduced crude ispreheated in the vapor heat exchanger 8 and tar heat exchanger 17 (alsoin exchanger 8', if desired), and is then passed continuously into thecracking coil 23 at a temperature of around 500 F. In the coil thetemperature of the oil is'raised to about 850 F., and at thistemperature it enters the drum or drums (27 and/or 28). The temperatureof the converted product passing from the drums may be 750 F. or'thereabout Vapors and liquid together are passed from the drum or drumsinto the still through the pipe 35.,

' .The pressure in the coll and drums may be, for example, about 300 to350 pounds per square inch. This pressure may be reduced through vtherelease valve 36 to substantially atmospheric pressure. The coolingincident to expansion of vapors may lower the temperature of the oilentering the still to about 700 F. The temperatures and pressuresreferred to abov'e are those generally preferred, but they may bevaried.. A pressure control valve may be installed in the line 9, foruse if it is desired to 'operate the still 1 and tower 5 under pressure.

In starting the operation, the still 1 is charged with reduced crude andfired to a distillation temperature. Reduced crude is supplied to thecracking coil, which is suitably fired. The eluent from the coil isdischarged into the drum or drums, and the cracked product is deliveredinto the still, in the manner described.

The cracking coil and soaking drums may be operated under an suitableconditions. Generally, the oil will be passed through the coil a't sucha velocity that most of any carbon forming therein is swept out into thedrums. Conversion takes place in the coil and drums, in a manner wellunderstood in the art; that is, incipient or partial conversion occursin the coil and further conversion is effected in the drum, by virtue ofthe contained heat of the oil.

The heat content of the oil from the drum is not sufficient to vaporizein the still theV amount of gas oil required for best results. Theproper amount of additional heat is therefore supplied to the still,preferably by passing hot combustion4 gases through its internal flues3. This method of heating is grade crudes which have been distilled orthe removal of gasoline. Without this heating the percentage yield ofgasoline from such stock is limited by two factors, namely the qualityvof the tar produced, and the amount of gas oil that 1s availableAforrecycling. If the digestion is conducted atsuch a temperature thatthe heat content of the digested oil is sufficient to vaporize anadequate amount of gas oil, the carbon. sediment content of the residuumor tar will generally be so high as'to prevent its use as fuel oil.Conversely, if the digestion is carried out at a temperature low enoughto insure ood'tar the amount of gas oil vaporized will Ee insufficient,and the yield of gasoline on recycling will be correspondinglydiminished.

Inaccordance with the resent invention, therefore, I suppl heat inependently to va- -porize the desire amount of gas oil. The

cracking is regulated to produce the maximum amount of gasoline` thatmay be obtained without causing the tar to produce too much sediment.The maximum amount ofsediment is usually 0.25%. '.Tar containin not morethan this amount will meet unker C specifications for fuel oil.' For 66nis cruv example when working with 55% Califorde bottoms (reducedcrude), without heating the still or chamber connected to thefractionating tower, the usual yields areabout 20% gasoline, 10% refinedoil, 20% gas oil, and 50% fuel oil capable of passing the standardsediment tests. The coke and glas loss is small and may be neglected forpresent purposes. The gas oil may be cracked with about 40% conversionto gasoline, making a total gasoline yield of 28%. With the heatedstill, the ,same initial a-mount of gasoline and refined oil may beobtained, but I take olf 40% of gas oil, the residuum being reduced to30%. With a 40% conversion of the gas oil to gasoline, the totalgasoline yield is 36%. In general, the still will be operated to produceat least 30% of gas oil.

The gas oil may be mixed with the reduced crude, if desired, and used asa feed stock for the ,same coil. It is generally preferred,

however, to crack the gas oil in a separate operation. The tar from thisoperation is available for blending with the tar from the reduced crudeto produce a desirable fuel oil product.

The advantages of the invention are not necessarily dependent uponspecific details of the construction and operation described, andvarious changes and alternative arrangements may be made within thescope of the appended claim, in which it is my intention to claim allnovelty inherent in the invention as broadly as the prior art permits.This application is a continuation in part of my application Serial No.45,195, filed July 22, 1925.

I claim:

Apparatus for cracking reduced crude oil comprising a cracking coil, adigesting drum connected to receive oil from the coil, a fractionatingdevice, a chamber connected with said device, internal flues for atleast partially heating the chamber, a connection for passing thecracked product directly and without substantial loss of heat from thedigesting drum into the chamber, means for separately withdrawing thegas oil fraction ,from the fractionating device, heat exchange coils inthe upper part of the 'fractionating device, a heat exchanger throughwhich the hot tar from the chamber is passed and means for supplying thereducedcrude through said heat exchange coils and heat exchangerto thecracking coil.

NATHANIEL E. LOOMIS.

